A Silicon Micromachined Resonant Angular Sensor

A silicon resonant angular rate sensor (gyroscope) with ring - disk - shaped resonator was fabricated using silicon bulk micromachining and its properties were investigated. The sensor consists of a glass-silicon-glass structure. The ring - disk - shaped silicon resonator has 3300μm×3100μm size and 30μm-thick. The resonator is suspended by four beams, and the ends of beams are anchored to a support which is in the center of the ring. The silicon structure was machined by alkali etching and reactive ion etching. Driving the resonator and detecting the vibration are performed by electrostatic forces and capacitive changes between the silicon resonator and electrodes on the glass. The resonant frequencies of the test device were 4.2kHz in driving mode and 3.5kHz in detecting mode. Although the difference in resonant frequencies between two modes was about 20%, a noise-equivalent rate of 3deg./sec was obtained at 7 Pa.